Most utility poles used today made of wood. Distribution utility poles are divided into ten classes, from 1 to 10. The classes' definition specifies a minimum circumference that depends on the species of tree and the length of the pole. This circumference is measured 6 feet from the butt of the pole. There is also a minimum top circumference that is the same for all species and lengths.
For example, a class 1 pole has a minimum top circumference of 27 inches. If it is 25 feet long and cedar (most utility poles are cedar), the circumference measured 6 feet from the bottom must be at least 43.5 inches.
The higher the class number, the skinnier the pole. Pole lengths start at 16 feet and increase by 2-foot steps to 22 feet, then by fives from 25 feet to 90 feet. A 90-foot class 1 western red cedar pole weighs about 6,600 pounds. A 16-foot pole weighs only about 700.
All utility poles used are pressure treated to preserve the wooden utility poles from the weather, insects and other types of attacks and decay. Utility poles are treated with a number of toxic chemicals including pentachlorphenol, chromated copper arsenate, creosote, copper azole and others.
Pentachlorophenol (Penta) is widely-used wood preservative that is normally dissolved in a petroleum carrier. It is the most commonly used preservative system utilized by North American utilities.
Chromated Copper Arsenate (CCA) is water-borne treatment that offers a wide range of advantages for treated lumber, timber and poles; clean; odorless; paintable. For poles, its use is limited to southern yellow pine, pinus sylvestris, and western red cedar.
Creosote is an oil-based wood preservative blended from the distillation of coal tar and comprised of more than 200 major constituents. Used in industrial applications, such as railroad ties, piling (both salt water and fresh water), and for utility poles.
Copper Azole (CA-B) is a water-borne copper based wood preservative with an organic co-biocide (Tebuconazol). Similar in color, to CCA-C, odorless, clean, paintable or stainable. Copper Azole is approved by the American Wood Preservers Association for use on Western Red Cedar and Southern Yellow Pine utility poles.
There are several problems associated with wooden utility poles. One problem is that utility poles are heavy and bulky and hard to move and install. Another problem is that wooden utility poles are treated with chemicals that are harmful to the environment, and poisonous (e.g. arsenic, etc.) to humans and animals and have been shown in some instance to cause cancers. Another problem is that even with pressure treating the wood, wooden utility poles have to be replaced or retreated about every ten years. Another problem is that wooden utility poles are not aesthetically pleasing to look and are typically all a brown or black color.
There are also problems associated with transmission towers to which high voltage electrical lines are attached. An electricity pylon or transmission tower is a tall, usually steel lattice structure used to support overhead electricity conductors for electric power transmission. The structure is usually made from lynx triangles because if another shape is used it would slowly bend out of shape without bending the joints. The result would be a bent or broken pylon. For example if a rectangle is used it would bend into the shape of a parallelogram due to the associated forces.
One problem is that transmission towers are hard to design, expensive to build and hard to maintain. The transmissions towers are subject to large forces including those related to the transmission components such as wires and cable and environmental forces such as wind, rain, snow, ice, etc.
Another problem is that transmission towers often require additional support. Yet another problem is that transmission towers are difficult for maintenance workers and technicians to climb.
There have been attempts to solve some of these problems. For example, U.S. Pat. No. 7,159,370 that issued to Oliphant, et al. entitled “Modular fiberglass reinforced polymer structural pole system” teaches “This invention is a modular pole assembly comprised of corner pieces and panel members. Panel members are slidably engaged to the corner pieces and are retained in a direction normal to the engagement direction by a track in each slot that nests within a groove in each panel member. Corner pieces may include multiple slots along each side, allowing for multiple layers of panel members along each side, thereby increasing strength and allowing an insulative and structural fill material to be added between panel member layers. The height of the modular pole may be increased by inserting splicing posts between consecutive, adjacent corner members and inserting splicing pieces between co-planar adjacent panel members. The modular nature of the pole assembly provides for simple packaging and shipment of the various components and easy assembly at or near the installation location.”
U.S. Pat. No. 6,453,635 that issued to Turner entitled “Composite utility poles and methods of manufacture” teaches “Composite utility pole structures and methods of manufacture using a pultrusion process. The poles may be N sided, with longitudinal pre-stressed rovings in each corner. The inner periphery of the poles may have flat regions centered between the outside corners, with the flat regions joined by circular arcs in the corner regions. Various pole structures and methods of manufacture are described, including curved poles and poles having walls that are tapered in thickness and structure.”
U.S. Pat. No. 6,357,196 that issued to McCombs entitled “Pultruded utility pole” teaches “A hollow fiberglass utility pole includes a pair of segments that are a fiberglass sheet that has a semicircular cross-section. The segments have first and second longitudinal edges with male and female couplers respective shapes that have a complimentary relationship to each other for mechanical engagement thereof. The fiberglass pole is assembled by engaging the first longitudinal edge of one segment with the second longitudinal edge of the other segment at an installation site. The fiberglass pole may be used as a sheath to encase an existing wooden pole.”
U.S. Pat. No. 5,311,713 that issued to Goodrich entitled Electric and telephone pole ground protector teaches “A device and method for protecting the end of a wooden utility pole set in the ground. A split cylindrical casing is provided which can be placed around the lower end of a wooden utility pole just before it is installed in the ground. The casing comprises an elongate, relatively thin cylindrical member having one closed end and being split into two sections connected together along the side thereof. The connection acts as a hinge. The edges of the casing where it is split are provided with a fastener, one part of the fastener being disposed along the edge of one part of the casing and another part of the fastener being disposed along the edge of the other part of the casing. When the cylindrical casing is closed, the edge of one part overlaps the edge of the other part so that the respective parts of the fasteners fit matingly together. Preferably, the fastener extends the entire length of the casing and entirely across the bottom end thereof. Preferably, the casing is made of high grade plastic.”
U.S. Pat. No. 5,175,971 that issued to Maccomb entitled ‘Utility power pole system” teaches “A utility power pole system comprises a pultruded hollow primary pole having an external hexogonal cross section and a number of longitudinal exterior grooves along its length. The hollow primary pole also has an internal hexogonal cross section rotated 30.degree. relative to the external hexagonal cross section. One or more pultruded hollow liners are provided which are also hexagonal in cross section and which may be internally or externally concentric with the primary pole. These liners vary in length to achieve an effective structural taper to the power pole system. The insertion of a tapered liner in the lower portion of the utility pole results in a utility pole having the effective load bearing capability of a tapered utility pole. By using a plurality of overlapping liners of varying lengths, an effective taper can be provided to the utility pole. The longitudinal grooves in the outer surface of the primary pole provide a means for climbing for a utility lineman and a means for attaching accessory attachment devices such as cross arms, stiffening members, conductor supports and for interconnection with other structural elements in a more extensive system. The rounded edges of each longitudinal groove are directed inwardly so as to retain devices in the groove which conform to the cross section of the groove. Cross arms attached to the utility pole may also employ similar longitudinal grooves to facilitate interconnection with existing utility hardware or other components.”
U.S. Pat. No. 4,803,819 that issued to Kelsey entitled “Utility pole and attachments formed by pultrusion of dielectric insulating plastic, such as glass fiber reinforced resin” teaches “a utility pole and attachments formed by pultrusion of dielectric insulating plastic, such as glass fiber reinforced resin.”
However, none of these solutions overcome all of the problems with utility poles and utility structures. Thus, it would be desirable to solve some of the problems associated with utility poles and utility structures such as transmission towers.